Inspection apparatus which inspects foreign substances mixed into powder materials have been proposed in the fields of medical products and food products by, for example, Japanese Examined Patent Application No. 48065/1995. As shown in FIG. 5, an apparatus 101 oscillates powder material P discharged from a hopper 103 with an oscillating plate 105, to supply a predetermined amount of the powder material P to a belt conveyor 107. A squeezee 109 arranged at the conveyor 107 scrapes the surface of the powder material P, to level the thickness of the powder material P. Thus, images of the powder material P having uniform thickness are obtained with a two-dimensional camera 111. The obtained images are subjected to image processing utilizing brightness differences, whereby foreign substances mixed into the powder material P are detected.
For more accurate inspection with the above-described apparatus, the space between the conveyor 107 and the squeezee 109 is minimized so as to reduce the thickness of the powder material P. However, the narrowed space between the conveyor 107 and the squeezee 109 adversely causes clogging of the powder material P.
The amount of the powder material P supplied to the conveyor 107 and conveying speed of the conveyor 107 should be adjusted in a well-balanced manner in order to supply a predetermined amount of the powder material P to the conveyor 107. Though, when the thickness of the powder material P is reduced, this adjustment becomes difficult, making it difficult to keep the supply amount of the powder material P fixed. The conveying speed of the conveyor 107 is a major factor in the clogging of the powder material P, making it difficult to control the supply amount of the powder material P. Thus, it was difficult to obtain uniform thickness in the powder material on the conveyor, which made it difficult to uniformly level the powder material surface to be inspected.
The present invention has been developed to solve the above-described problems. An objective of the present invention is to provide a foreign substance inspection apparatus with high operating reliability which enables highly-accurate inspection of the intermixing of foreign substances.